1. Field of the Invention
This invention relates to an ink jet type recording apparatus in which its recording head is moved in the direction of width of a recording sheet, and ink droplets are jetted onto the recording sheet in accordance with printing data, to form an image thereon, and more particularly to a capping device suitable for sealing the recording head, and to a pump unit for supplying negative pressure to the capping device.
2. Description of the Related Art
An ink jet type recording apparatus in which, with ink pressurized in a pressurizing chamber, ink droplets are jetted onto the recording sheet thereby to record printing data, suffers from difficulties that, because of evaporation of solvent from the nozzle opening, the ink is increased in viscosity, or solidified, or foreign matters such as dust stick onto the nozzle opening, and because of the formation of bubbles in the ink, the resultant print is unacceptable. In order to overcome the above-described difficulties, the ink jet type recording apparatus has capping means for sealingly closing the nozzle opening when the apparatus is not in operation, and cleaning means for cleaning the nozzle plate when necessary.
The teachings of Japanese Patent Application (OPI) No. 125239/1989 (the term "OPI" as used herein means an "unexamined publication application") disclose an ink jet type recording apparatus having a sled which is pushed and moved by the carriage moving to the home position. The sled is moved along a sloped guide surface of a frame to the nozzle opening surface of the recording head, so that a rubber cap formed on the surface of the sled is pressed against the recording head to sealingly close the nozzle opening.
Furthermore, Japanese Patent Application Publication No. 13910/1990 disclosed the following ink jet type recording apparatus: In the apparatus, in order to press a cap against the recording head, two arms forming a parallelogram link are interposed between the frame and the cap, so that the cap is moved horizontally by the carriage while being moved vertically towards the head.
The amounts of vertical movement of the above-described means are determined by the sloped guide surface of the frame, and the parallelogram link, respectively. Therefore, in the case where the distance between the path of movement of the carriage and the frame is somewhat varied because of tolerances in machining or assembling the components, or in the case where, in order to print data on a recording sheet relatively large in thickness such as an envelope, the distance between the platen and the recording head is adjusted, thus changing the distance between the recording head and the cap. Hence, the sealing of the nozzle opening depends on the elastic deformation of the cap itself. This poses no problem in the case where the surface to be sealed is small; however, it is considerably difficult to uniformly seal the entire surface of a recording head having a number of nozzles.
The teachings of Japanese Patent Application (OPI) No. 103762/1984 disclose the following means: At the home position of the carriage, an inverted-L-shaped head protective cover having a cap at one end is swingably supported. The protective cover is swung by the carriage when moved to the home position, so that its cap is pressed against the recording head. With the above-described means, the amount of swing of the protective cover changes according to the distance to the nozzle surface. Hence, the means can provide a positive sealing effect even for the recording apparatus which is so designed that the distance between the platen and the printing head is adjustable. However, it suffers from the following problem: Since the direction of movement of the recording head is different from that of the cap, the relative movement of the recording head and the cap may deform the latter; that is, the cap is liable to be broken.